[PATCH v4 00/59] struct filename series

Al Viro
2026-01-08T07:36:48Z

[See https://lore.kernel.org/all/20251216035518.4037331-1-viro@zeniv.linux.org.uk/
for previous variant]

Changes compared to v3:
* rebased to v6.19-rc4
* the size of embedded name is increased to the point where struct filename
is 192 bytes long
* introduction of CLASS machinery moved up by several commits, so
that "allow incomplete imports of filenames" could make use of it immediately;
as the result, a couple of followups in io_uring/* fold into it.
* __getname_maybe_null() makes use of CLASS(filename_flags)
* calls of refname() (all 3 of them, all in kernel/auditsc.c) expanded.
* convert init_mkdir() et.al. to use of do_mkdirat() and friends, similar
to how init_rmdir() and init_unlink() are done.

Practically all destructor calls are done via CLASS(filename...) now;
only 3 explicit calls left (one in audit, dropping the references it has
grabbed for itself, two in the vicinity of fsconfig - separate story).
No uses of __free(putname) remain; I haven't removed DEFINE_FREE yet,
but it's really tempting.

I've got some continuations for that series (non-consuming variants of
do_renameat2() and friends, now that it can be done with minimal PITA
in the callers; with that added we get almost all constructors done via
CLASS(...); the only exceptions are around fsconfig), but that's in
a separate branch (#experimental.filename) on top of this one.

The branch lives in
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git #work.filename
now; individual patches in followups.

Please, review; if nobody objects, I'm putting that in #for-next on Saturday.

Rough overview:
1--9:
moving pathname import out of retry loops
10:
now we can get rid of "reuse the struct filename if
we'd just imported it from the same address _and_ audit is
enabled" logics.
11:
get rid of names_cachep abuse in ntfs
12--15:
embed reasonably short pathnames into struct filename,
*always* get struct filename out names_cachep, take the long
names into explicitly kmalloc'ed objects.
16:
runtime_const machinery for names_cachep; there's
a potentially better variant (statically allocated kmem_cache),
but that's a separate series.
17:
infrastructure for CLASS(filename...)
18:
switch __getname_maybe_null() to that.
19:
delayed_filename machinery, solves the audit vs. io_uring
problems.
20:
now we don't need filename->refcnt to be atomic.
21--25:
simplify checks in callers of pathwalk primitives -
they (with exception of do_filp_open()) will do
the right thing if given ERR_PTR() for name.
26--32: ... get rid of that one exception and simplify
more callers.
33--56:
conversions to CLASS(filename...), cleanups
57, 58:
... and these should not have been using getname().
59:
trimming fs/init.c down - doing to init_mkdir() et.al. what's
already been done to init_rmdir() and init_unlink().

Shortlog:
Al Viro (58):
do_faccessat(): import pathname only once
do_fchmodat(): import pathname only once
do_fchownat(): import pathname only once
do_utimes_path(): import pathname only once
chdir(2): import pathname only once
chroot(2): import pathname only once
user_statfs(): import pathname only once
do_sys_truncate(): import pathname only once
do_readlinkat(): import pathname only once
get rid of audit_reusename()
ntfs: ->d_compare() must not block
getname_flags() massage, part 1
getname_flags() massage, part 2
struct filename: use names_cachep only for getname() and friends
struct filename: saner handling of long names
allow to use CLASS() for struct filename *
switch __getname_maybe_null() to CLASS(filename_flags)
allow incomplete imports of filenames
struct filename ->refcnt doesn't need to be atomic
file_getattr(): filename_lookup() accepts ERR_PTR() as filename
file_setattr(): filename_lookup() accepts ERR_PTR() as filename
move_mount(): filename_lookup() accepts ERR_PTR() as filename
ksmbd_vfs_path_lookup(): vfs_path_parent_lookup() accepts ERR_PTR() as name
ksmbd_vfs_rename(): vfs_path_parent_lookup() accepts ERR_PTR() as name
do_filp_open(): DTRT when getting ERR_PTR() as pathname
rename do_filp_open() to do_file_open()
do_sys_openat2(): get rid of useless check, switch to CLASS(filename)
simplify the callers of file_open_name()
simplify the callers of do_open_execat()
simplify the callers of alloc_bprm()
switch {alloc,free}_bprm() to CLASS()
file_[gs]etattr(2): switch to CLASS(filename_maybe_null)
mount_setattr(2): don't mess with LOOKUP_EMPTY
do_open_execat(): don't care about LOOKUP_EMPTY
vfs_open_tree(): use CLASS(filename_uflags)
name_to_handle_at(): use CLASS(filename_uflags)
fspick(2): use CLASS(filename_flags)
do_fchownat(): unspaghettify a bit...
chdir(2): unspaghettify a bit...
do_utimes_path(): switch to CLASS(filename_uflags)
do_sys_truncate(): switch to CLASS(filename)
do_readlinkat(): switch to CLASS(filename_flags)
do_f{chmod,chown,access}at(): use CLASS(filename_uflags)
do_{renameat2,linkat,symlinkat}(): use CLASS(filename_consume)
do_{mknodat,mkdirat,unlinkat,rmdir}(): use CLASS(filename_consume)
namei.c: convert getname_kernel() callers to CLASS(filename_kernel)
namei.c: switch user pathname imports to CLASS(filename{,_flags})
filename_...xattr(): don't consume filename reference
move_mount(2): switch to CLASS(filename_maybe_null)
chroot(2): switch to CLASS(filename)
quotactl_block(): switch to CLASS(filename)
statx: switch to CLASS(filename_maybe_null)
user_statfs(): switch to CLASS(filename)
mqueue: switch to CLASS(filename)
ksmbd: use CLASS(filename_kernel)
alpha: switch osf_mount() to strndup_user()
sysfs(2): fs_index() argument is _not_ a pathname
switch init_mkdir() to use of do_mkdirat(), etc.

Mateusz Guzik (1):
fs: hide names_cache behind runtime const machinery

Diffstat:
arch/alpha/kernel/osf_sys.c | 34 ++--
fs/dcache.c | 8 +-
fs/exec.c | 99 ++++------
fs/fhandle.c | 5 +-
fs/file_attr.c | 12 +-
fs/filesystems.c | 9 +-
fs/fsopen.c | 6 +-
fs/init.c | 88 +--------
fs/internal.h | 5 +-
fs/namei.c | 370 ++++++++++++++++++++------------------
fs/namespace.c | 22 +--
fs/ntfs3/dir.c | 5 +-
fs/ntfs3/fsntfs.c | 4 +-
fs/ntfs3/inode.c | 13 +-
fs/ntfs3/namei.c | 17 +-
fs/ntfs3/xattr.c | 5 +-
fs/open.c | 119 +++++-------
fs/quota/quota.c | 3 +-
fs/smb/server/vfs.c | 15 +-
fs/stat.c | 28 +--
fs/statfs.c | 3 +-
fs/utimes.c | 8 +-
fs/xattr.c | 33 +---
include/asm-generic/vmlinux.lds.h | 3 +-
include/linux/audit.h | 11 --
include/linux/fs.h | 42 +++--
io_uring/fs.c | 101 ++++++-----
io_uring/openclose.c | 26 +--
io_uring/statx.c | 17 +-
io_uring/xattr.c | 30 ++--
ipc/mqueue.c | 11 +-
kernel/acct.c | 4 +-
kernel/auditsc.c | 29 +--
mm/huge_memory.c | 15 +-
mm/swapfile.c | 21 +--
35 files changed, 483 insertions(+), 738 deletions(-)